/*******************************************************************************
 * Copyright 2011, 2012 Chris Banes.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the
 * License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations
 * under
 * the License.
 *******************************************************************************/
package com.goldplusgold.support.lib.widget.pulltorefresh;

import android.annotation.TargetApi;
import android.view.View;

import com.goldplusgold.support.lib.widget.pulltorefresh.PullToRefreshBase.Mode;
import com.goldplusgold.support.lib.widget.pulltorefresh.PullToRefreshBase.State;

@TargetApi(9)
public final class OverscrollHelper {

    static final String LOG_TAG = "OverscrollHelper";
    static final float DEFAULT_OVERSCROLL_SCALE = 1f;

    /**
     * Helper method for Overscrolling that encapsulates all of the necessary function. <p/> This
     * should only be used on AdapterView's such as ListView as it just calls through to
     * overScrollBy() with the scrollRange = 0. AdapterView's do not have a scroll range (i.e.
     * getScrollY() doesn't work).
     *
     * @param view         - PullToRefreshView that is calling this.
     * @param deltaX       - Change in X in pixels, passed through from from overScrollBy call
     * @param scrollX      - Current X scroll value in pixels before applying deltaY, passed
     *                     through
     *                     from from overScrollBy call
     * @param deltaY       - Change in Y in pixels, passed through from from overScrollBy call
     * @param scrollY      - Current Y scroll value in pixels before applying deltaY, passed
     *                     through
     *                     from from overScrollBy call
     * @param isTouchEvent - true if this scroll operation is the result of a touch event, passed
     *                     through from from overScrollBy call
     */
    public static void overScrollBy(final PullToRefreshBase<?> view, final int deltaX, final int scrollX,
                                    final int deltaY, final int scrollY, final boolean isTouchEvent) {
        overScrollBy(view, deltaX, scrollX, deltaY, scrollY, 0, isTouchEvent);
    }

    /**
     * Helper method for Overscrolling that encapsulates all of the necessary function. This
     * version
     * of the call is used for Views that need to specify a Scroll Range but scroll back to it's
     * edge
     * correctly.
     *
     * @param view         - PullToRefreshView that is calling this.
     * @param deltaX       - Change in X in pixels, passed through from from overScrollBy call
     * @param scrollX      - Current X scroll value in pixels before applying deltaY, passed
     *                     through
     *                     from from overScrollBy call
     * @param deltaY       - Change in Y in pixels, passed through from from overScrollBy call
     * @param scrollY      - Current Y scroll value in pixels before applying deltaY, passed
     *                     through
     *                     from from overScrollBy call
     * @param scrollRange  - Scroll Range of the View, specifically needed for ScrollView
     * @param isTouchEvent - true if this scroll operation is the result of a touch event, passed
     *                     through from from overScrollBy call
     */
    public static void overScrollBy(final PullToRefreshBase<?> view, final int deltaX, final int scrollX,
                                    final int deltaY, final int scrollY, final int scrollRange, final boolean isTouchEvent) {
        overScrollBy(view, deltaX, scrollX, deltaY, scrollY, scrollRange, 0, DEFAULT_OVERSCROLL_SCALE, isTouchEvent);
    }

    /**
     * Helper method for Overscrolling that encapsulates all of the necessary function. This is the
     * advanced version of the call.
     *
     * @param view           - PullToRefreshView that is calling this.
     * @param deltaX         - Change in X in pixels, passed through from from overScrollBy call
     * @param scrollX        - Current X scroll value in pixels before applying deltaY, passed
     *                       through
     *                       from from overScrollBy call
     * @param deltaY         - Change in Y in pixels, passed through from from overScrollBy call
     * @param scrollY        - Current Y scroll value in pixels before applying deltaY, passed
     *                       through
     *                       from from overScrollBy call
     * @param scrollRange    - Scroll Range of the View, specifically needed for ScrollView
     * @param fuzzyThreshold - Threshold for which the values how fuzzy we should treat the other
     *                       values. Needed for WebView as it doesn't always scroll back to it's
     *                       edge.
     *                       0 = no fuzziness.
     * @param scaleFactor    - Scale Factor for overscroll amount
     * @param isTouchEvent   - true if this scroll operation is the result of a touch event, passed
     *                       through from from overScrollBy call
     */
    public static void overScrollBy(final PullToRefreshBase<?> view, final int deltaX, final int scrollX,
                                    final int deltaY, final int scrollY, final int scrollRange, final int fuzzyThreshold,
                                    final float scaleFactor, final boolean isTouchEvent) {

        final int deltaValue, currentScrollValue, scrollValue;
        switch (view.getPullToRefreshScrollDirection()) {
            case HORIZONTAL:
                deltaValue = deltaX;
                scrollValue = scrollX;
                currentScrollValue = view.getScrollX();
                break;
            case VERTICAL:
            default:
                deltaValue = deltaY;
                scrollValue = scrollY;
                currentScrollValue = view.getScrollY();
                break;
        }

        // Check that OverScroll is enabled and that we're not currently
        // refreshing.
        if (view.isPullToRefreshOverScrollEnabled() && !view.isRefreshing()) {
            final Mode mode = view.getMode();

            // Check that Pull-to-Refresh is enabled, and the event isn't from
            // touch
            if (mode.permitsPullToRefresh() && !isTouchEvent && deltaValue != 0) {
                final int newScrollValue = (deltaValue + scrollValue);

                if (newScrollValue < (0 - fuzzyThreshold)) {
                    // Check the mode supports the overscroll direction, and
                    // then move scroll
                    if (mode.showHeaderLoadingLayout()) {
                        // If we're currently at zero, we're about to start
                        // overscrolling, so change the state
                        if (currentScrollValue == 0) {
                            view.setState(State.OVERSCROLLING);
                        }

                        view.setHeaderScroll((int) (scaleFactor * (currentScrollValue + newScrollValue)));
                    }
                } else if (newScrollValue > (scrollRange + fuzzyThreshold)) {
                    // Check the mode supports the overscroll direction, and
                    // then move scroll
                    if (mode.showFooterLoadingLayout()) {
                        // If we're currently at zero, we're about to start
                        // overscrolling, so change the state
                        if (currentScrollValue == 0) {
                            view.setState(State.OVERSCROLLING);
                        }

                        view.setHeaderScroll((int) (scaleFactor * (currentScrollValue + newScrollValue - scrollRange)));
                    }
                } else if (Math.abs(newScrollValue) <= fuzzyThreshold
                        || Math.abs(newScrollValue - scrollRange) <= fuzzyThreshold) {
                    // Means we've stopped overscrolling, so scroll back to 0
                    view.setState(State.RESET);
                }
            } else if (isTouchEvent && State.OVERSCROLLING == view.getState()) {
                // This condition means that we were overscrolling from a fling,
                // but the user has touched the View and is now overscrolling
                // from touch instead. We need to just reset.
                view.setState(State.RESET);
            }
        }
    }

    static boolean isAndroidOverScrollEnabled(View view) {
        return view.getOverScrollMode() != View.OVER_SCROLL_NEVER;
    }
}
